1. Field of the Invention
The present invention is generally directed to the field of packaging and containers, and particularly to plastic containers of the type having closable covers which are intended to be repeatedly closed and reopened. The present invention is specifically directed to a container having a positive locking mechanism which prevents the cover from accidentally opening when the container is dropped or impacted.
2. Description of the Prior Art
A variety of products are now commonly packaged in reclosable plastic containers with the expectation that the consumer will retain the container for a period of time to store the purchased articles. Consequently, such containers must be capable of withstanding a reasonable number of cycles of opening and closing during the expected period of use of the articles. The functioning of the container, particularly the ease by which the container may be closed and reopened, thus becomes an important factor in total consumer satisfaction.
A typical plastic container intended to hold merchandise at the point of sale has a bottom portion or base and a top portion or cover attached to the base by a hinge. Although rectangular packages are most common, the base and cover may have a variety of configurations including polygonal, round and oblong. To hold the cover to the base when the cover is closed, it is very common to provide some means for interlocking the cover and base. One type of interlocking structure is obtained by providing an upstanding shoulder about the periphery of the base which has an outwardly extending, overhanging lip. The cover has a depending wall portion with an indentation therein adapted to mate with the lip on the base so that when the cover is pressed to the base, the indentation and lip engage with each other in a "snap" fit. The engagement between the lip and indentation holds the cover and base together during normal handling but allows them to be parted when sufficient force pulling them apart is exerted.
For many containers having a secure snap-fit closure, it may be difficult or inconvenient for the user to reopen the container simply by grabbing the two halves and pulling them apart. For example, the base and cover portions may not be readily grasped by the hands of the user; the base and cover may be too large or too small or too slippery or in a shape which is difficult to hold; or under some circumstances, it may be desirable or even necessary for the user to be able to open the container using only one hand. The finger manipulation required to pull such flanges apart may also present problems to some users, such as those afflicted with arthritis.
Consequently, many of the presently available reclosable containers have some feature formed on them specifically intended to aid the user in reopening the container. For example, it is common for containers to be provided with flanges which extend outwardly from the peripheries of the base and cover portions. Usually, the flanges are formed adjacent one another but do not entirely overlap. The user may then pull the flange portion on the cover and base away from each other with his fingers to draw the cover and base apart. An example of such a container is found in U.S. Pat. No. 4,202,464 to Mohs et al.
Other containers utilize a locking mechanism in which one portion of the container, e.g., the cover, contains a hook-like piece and the other portion, for example the base, contains a co-acting latching mechanism designed to fit over the locking hook. An example may be found in U.S. Pat. No. 4,079,880 to Edwards. U.S. Pat. No. 4,314,651 to Gaiser et al. is similar to Edwards in that the lid portion is provided with an upwardly depending locking hook and the base portion is provided with a latching mechanism to fit over the hook. Similarly, U.S. Pat. No. 4,096,986 to Florian discloses a foamed plastic food tray having a cover and a base. The base has a slotted hook-like mechanism and the cover has a projecting flute with a flared out terminus designed to interact with the hook-like mechanism.
U.S. Pat. No. 4,582,248 to Bixler et al. discloses a thermoformed one-piece container in which the base portion has an outwardly depending locking hook designed to fit within a corresponding lock opening of the cover portion. Additionally, U.S. Pat. No. 3,817,419 to Moller et al. discloses a locking mechanism for a one-piece container where the lid and base portions are hingedly connected. The base portion is provided with a downwardly depending member having a locking hook, and the cover portion has a latching mechanism designed to be positively latched to the locking hook of the base portion. The cover is secured to the base by pushing the latching mechanism onto the locking hook. While these patents solve many of the problems relating to securing covers to containers, they still suffer the deficiency of being difficult to open, especially by those not mechanically adept to such practice.
In an effort to overcome some of the above-mentioned problems, U.S. Pat. No. 4,602,719 to Borst provides a reclosable plastic container in which the cover may be attached to the base by an interlocking structure having release tabs on each of the cover and base. The release tabs have camming surfaces which intersect with each other. When the tabs are pressed together, they rotate about a fulcrum created by the intersecting camming surfaces to pull the cover and base apart. While this patent represents an advance over the other prior art patents, it still suffers the deficiency of not providing a positive locking mechanism. By this, it is meant that the lock does not positively interact with a latching mechanism to prevent the cover from separating from the base if the container is dropped or impacted in some way.